1. Field of the invention
The invention relates to a conveyor comprising an endless elastic conveyor belt having a conveyor surface, guide rollers around which the conveyor belt passes to define a conveying portion and a returning portion of the belt, support means, such as a series of spaced rollers, for supporting the returning portion, and a plurality of stops spaced longitudinally apart on the conveyor surface for engaging material carried by the conveying portion of the belt to prevent or halt slippage of the material on the belt.
2. Summary of the prior art
My U.S. patent application Ser. No. 336,330 filed Apr. 11, 1989 discloses a conveyor of the above type having a plurality of tongues formed in the conveyor belt at longitudinally spaced intervals in the direction of travel of the belt, each of the tongues being formed by slits in the belt and having two longitudinal side edges, a trailing transverse edge with respect to the direction of travel of the conveyor belt, and a leading edge transition portion disposed substantially parallel to the trailing transverse edge and merging flush into the belt, the stops being disposed on the tongues in the region of the trailing transverse edges thereof. Although this conveyor has demonstrated its ability to transport material in a particular direction, when that direction is reversed the stops on the returning portion of the belt run up against the support rollers, squashing the tongues and causing the conveyor surface to tear.
The German journal "Gummi und Asbest" (at 1956, page 75) shows a conveyor comprising an endless conveyor belt passing around guide rollers and provided with a plurality of dogs spaced at intervals on the conveyor surface having wedge-shaped run-on and run-off surfaces which cause the returning portion of the belt to adopt a wave-like motion when guided over its support rollers. The dogs, in this arrangement, consist of a rectangular bar having run-on and run-off surfaces at opposite ends which, according to a particular embodiment, are of semi-circular or angular design, both surfaces gradually merging with the conveyor surface. The wave-like motion of the returning portion of the belt caused by the continual running-up of the dogs against the support rollers has been found, however, to communicate itself to the rest of the conveyor belt, having a detrimental effect on the material carried by the belt and leading to possible damage of sensitive materials.